The present invention pertains generally to support structures for sleeping, and to sleep systems which have combinations of support structures with varying support characteristics.
Devices for supporting the human body while sleeping have evolved generally from pads, to pads in combination with or supported by springs such as the common mattress, and further in combination with stiffer springs such as in mattress foundations or box springs. In a conventional mattress, springs or coils are interconnected in a matrix array, and covered on each side with layers of padding and fabric. Much of the innovation in mattresses and box springs is in the area of spring design, seeking configurations which provide optimal support of the body, in combination with the padding layers. There are certain design constraints on mattresses innersprings, such as the gauge of wire of the coils, the diameter, height, and number of coils in the array.
There is greater design flexibility in the material layers which cover the springs. There are conventionally one or more layers of non-woven insulation material over the terminal ends of the coils, one or more layers of polymer foam, and a quilted upholstery material. Typically both sides of the innerspring are provided with multiple layers of polymer foams, fiber batting and fabric layers of upholstery material, although some one-sided mattresses have been made. In general, mattresses are turned over periodically to avoid the setting or compaction of the polymer foam and fibrous material layers. The coils of the innerspring will not generally take a set, or in other words permanently compress to a reduced overall height. Therefore, turning the mattress simply relieves the material layers from repeated compression to allow return to the original shape. Because of this established practice of turning the entire mattress to the opposing side, both sides must be equally constructed symmetrically, with the same layers of material. This adds significantly to both the material, weight and manufacturing costs of the products.
In a one-sided mattress, the underside of the mattress innerspring is covered only minimally with inexpensive non-woven material. Often, there are also included layers of foam materials to create the visual perception of a full two-sided mattress, but which do not contribute to the support or comfort function of the mattress. The padded or sleep side is preferably constructed with materials which will resist taking a set, such as polymer foams and synthetic fiber batts. These mattresses may suffer in quality from the need to eliminate fibrous cushioning material which will compress, such as wool, synthetic and natural fibers, cotton and polyester. Certain types of foam such as polyurethanes and latex (which may be particularly thick) are added to provide cushioning. However, the foam materials did not have the distinct feel and comfort properties of fiber based cushioning.
In recent years, a significant portion of the additional mattress padding has been placed in the so-called pillowtop, i.e., an enclosed panel containing multiple layers of various foams and fiber batting which is sewn or otherwise fixedly attached to both sides of the mattress innerspring. See, for example, U.S. Pat. No. 5,787,532. For permanent attachment to the mattress innerspring upholstery, a gusset is formed to extend from the underside of the pillowtop, which is sewn to a mating gusset of the mattress upholstery material, along a tape edge of the pillowtop. Placing most of the comfort forming material (specifically, the fibrous materials) in permanently attached pillowtops on both sides of the mattress also requires that the mattress be periodically turned over to maintain its original shape. This turning is made increasing difficult by greater numbers of layers of material, and by the sheer size and weight of the mattress. The approach also necessitates that equal numbers of compressible material layers be included on both sides of the innerspring, adding significantly to the cost of the mattress.
A large number of layers of material in the pillowtop, including high density foam, natural and man made fiber batts, in combination with other padded or quilted upholstery, has made pillowtops very bulky and rounded at the edges. High bulk material layers, such as high-density foam, directly affect the height of the mattress, and the total height when combined with a foundation and bed frame. As a result, a separate border section is used, requiring two tape edge perimeters to be sewn on each side. It is a difficult assembly to sew together around the periphery with a tape edge, requiring expert operation of a large sewing machine mounted at an oblique angle to the mattress. The sewing head must of course traverse the entire perimeter of the mattress. In the case of mattresses with bordered pillowtops, this sewing process is required four to six times, to create two tape seams for each pillowtop (both sides) and two tape seams for both sides of the mattress. The labor cost is substantial. Also, in these constructions, the interface between the mattress or upholstery of the mattress innerspring and the pillowtop is always fabric-to-fabric, as either stitching or other form of fastening is used to maintain the alignment of the pillowtop with the mattress innerspring.
Other attempts have been made to attach pillowtops to mattress innersprings. See, for example, U.S. Pat. No. 4,809,375 describing an outer mattress cover attached to a deck cover at peripheral edges by zippers; U.S. Pat. No. 4,449,261 describing a removable and reversible pillowtop attached to the mattress by peripheral fastening means, and U.S. Pat. No. 4,955,095 describing a removable one-sided pillowtop attachable to a mattress innerspring by hook and loop fasteners. The pillowtops of these designs are essentially one-sided, having an asymmetrical arrangement of internal layers, and all use a separate mechanical fastening mechanism for attachment to the innerspring. Thus the problem of set formation or compression in the pillowtop can only be addressed by detaching and fluffing rather than turning the pillow top over. The necessity of having to release multiple fasteners adds to the labor of maintaining the mattress. Most importantly, these designs are significantly more difficult and expensive to produce than conventional sewn pillowtop attachment due to the added cost of the fastening devices, plus the manufacturing operations required to add the fastening devices. Moreover, the fasteners are apparent to touch and are visually unattractive. They also restrict comfort by not allowing the pillow to function as a free and independent element relative to the innerspring. These are major disadvantages of mattress pillow tops of the prior art.
The present invention provides a functionally integrated sleep system in which a comfort unit, containing multiple layers of fabric, fiber and foam materials, is held in place by friction upon an innerspring support unit which is placed upon a foundation. Alternatively, a separate frictional layer may be provided between a top comfort unit and an underlying support unit, wherein the top two units are maintained in alignment by the frictional property of the intermediate layer. A top surface of the innerspring support unit is constructed of a material which has a coefficient of friction with an upholstery material of the overlying comfort unit sufficient to prevent lateral or sliding movement of the comfort unit upon the innerspring support unit. This frictional engagement of the two sleep system components eliminates the need for fasteners therebetween, thus making the comfort unit usable on both sides, and easily exchangeable with comfort units of differing material construction and feel. The friction mounted comfort unit, being the only portion of the sleep system which will take a set or pronounced compression, can be freely removed from the system in a vertical direction to be flipped over or fluffed back to its original state. With the majority of comfort material layers contained in the freely mounted comfort unit, the innerspring support unit does not have to be combined with bulky material layers. The innerspring support unit provides the mechanical support function of mechanical coiling and recoiling of the individual springs in response to a load on the overlying comfort unit. The foundation provides reflexive support of both the innerspring support unit and the comfort unit.
In accordance with one general aspect of the invention, there is provided a sleep system which has a foundation unit, a support unit, and a comfort unit, wherein the comfort unit contains compressible material encapsulated in upholstery which is frictionally engaged with a supporting surface of the support unit to prevent lateral, longitudinal or sliding movement of the comfort unit when in contact with the support unit. The foundation unit includes a structural frame and one or more reflexive elements to provide a stiff flexural base for the support unit. The support unit (also referred to herein as a xe2x80x9csupport unitxe2x80x9d or xe2x80x9cinnerspring unitxe2x80x9d) includes an innerspring made of a plurality of springs or coils connected together in an array. The support unit may alternatively be a high performance high support factor foam core structure without any internal wire or spring elements. The support unit is covered with material on an underside and perimeter sides. A top-supporting surface of the support unit is covered with a frictional material which engages the upholstery material of a comfort unit positioned upon the support unit. The comfort unit is dimensioned to fit upon the supporting surface of the support unit, and contains one or more internal layers of compressible material encased in upholstery. The frictional material on the supporting surface of the support unit is in one embodiment a non-woven fabric with a polymeric coating. The upholstery of the comfort unit is a woven material which may also have a padded backing and be quilted. Fibers of the woven fabric of the comfort unit upholstery frictionally engage with the polymeric coating of the support unit covering to prevent lateral movement of the comfort unit in contact with the support unit. The comfort unit can be lifted vertically from the support unit, without release of any fasteners, to be turned over or replaced with a different support unit, e.g., having different internal padding materials or mechanical or electrical or electronic features such as vibration/massage, heat generation, pressure sensing, pressure application with controlled air bladders, or other internal monitoring or comfort adjustment devices or mechanisms.
In accordance with another aspect of the invention, there is provided a modular sleep system which includes a foundation unit, a support unit having an innerspring with a plurality of coiled springs, and a comfort unit frictionally engaged upon a support surface of the support unit. The comfort unit contains substantially all of the compressible material of the sleep system, such as foam and fiber layers, woven and non-woven. The comfort unit is freely removable from the support unit in a vertical direction, without detachment of any fasteners, to readily enable flipping, rotation or exchange with a different comfort unit. The support unit, having an innerspring core of wire-formed springs or coils, does not take a permanent set and therefore is not required to be turned. The substantial weight of the support unit is left stationary upon the foundation unit, while the comfort characteristics of the sleep system are maintained by handling only of the comfort unit. The frictional engagement of the upholstery of the comfort unit with a coated or frictional material which covers the supporting surface of the support unit prevents lateral movement or sliding of the comfort unit relative to the support unit. A conventional fitted bed sheet fits over both the comfort unit and the support unit.
These and other aspects of the present invention are herein described in further detail, with reference to the accompanying Figures, the illustrated embodiments being representative of only some of they ways in which the principles and concepts of the invention can be executed and employed.